Each character will have a set of side quests that you are going to complete for them if you want 100% completion of Code Vein.
Self-Important Revenant Side Quest Guide
Request 1: Ruined City Center – Parking Garage
After you have completed the whole Ruined City Center area, go to the Garage mistle. He is going to request you to defeat one of the Losts in Park Ruins which is proving out to be an obstruction for him.
You are going to travel to Park Ruins to defeat her and after defeating her, return back to the Garage. Inform Self-Important Revenant about it and you are going to complete your quest.
Request 2: Dried-Up Trenches – Decayed Ship Interior
When you interact with Self-Important Revenant here, he is going to tell you about the blood spring he is searching for. Once you offer him to check the location he is going to give you the Cliffs of Rest map.
As this is a Depths location, you would have to go to Davis in order to access the location. Go to the location, kill the monster, clear out the area and inform him about it in order to complete the quest.
Request 3: Ruined City Center – Poisonous Butterfly Nest
You are going to meet Self-Important Revenant in the Poisonous Butterfly Nest where he is going to tell ask for an activated mistle. You have to travel to Memories of Research Facility Area mistle and look for an area on your east which has people. You are going to find the Mistle Agent there located to the left of Silva and give it to the Self-Important Revenant to complete the quest.